A certain class of low power electronic devices may be used in the industry for measuring physical process values such as pressure, temperature, flow, and levels. An example of such electronic control device may be a process transmitter, also known as a field device. The field devices are frequently used for process instrumentation, which are used for instance to detect and/or influence process variables. The field devices are connected to one another by an automation network for the purpose of exchanging data. Field devices, which detect a physical or chemical variable as a process variable, convert a relevant variable into a measured value and output this measured valve to a central control station for further processing. Examples of measuring transducers of this type are measuring transducers for fill level, mass flow rate, pressure, temperature, pH value, conductivity, etc. Such low power electronic devices may include a display unit (e.g., Liquid Crystal Display (LCD)), a processing unit, a communication unit, and an input unit. Such electronic devices may contain an analog frontend including the sensors/transducers and a transmitter system, which is dedicated to the communication with the central control station. The communication may be performed in an analog mode (e.g., 4-20 mA) or a digital mode. The communication may be carried over bus systems such as ProfiBus, HART, Fieldbus foundation, and the like.
The display unit of such electronic devices may include a Graphics Liquid Crystal Display (GLCD), a plurality of backlight LEDs, and associated enabling circuitry. The GLCD includes a number of pixels configured to display alphanumeric characters. The display unit is powered by the transmitter board of the electronic device itself. Due to the various standards for process transmitters, the power and voltage supplied from the transmitter board are limited to small values.
The GLCD and the backlight LEDs of the display unit of such process transmitters consume a majority of the total allocated power for the field device. Therefore, the remaining functions of the field device, which includes power supply and logic circuitry, need to be optimized to consume remaining power. The GLCD consumes minimum power when operated at an optimum voltage level. The electronic devices may be powered by a variable supply, for example, a current loop (which also serves for signaling purposes). It is therefore important to regulate the supply provided to the display unit to the optimum voltage level. Therefore, there is a need for regulating the supply voltage to the particular voltage level in order to power the display unit, which includes the GLCD.
Currently, off-the-shelf voltage step-down and voltage step-up (e.g., buck-boost) converters may be configured to provide a constant output by processing supply voltages fluctuating between a range. An exemplary buck-boost converter may be TPS63036 manufactured by Texas instruments. The efficiency of TPS63036 is low for certain voltage ranges.